Quantum interfaces

Rational agents acting as observers use “knowables” to construct a vision of the outside world. Thereby, they are bound by the information exchanged with what they consider to be objects. The cartesian cut or, in modern terminology, the interface mediating this exchange, is again a construction. It serves as a “scaffolding,” an intermediate construction capable of providing the necessary conceptual means. An attempt is made to formalize the interface, in particular the quantum interface and quantum measurements, by a symbolic information exchange. A principle of conservation of information is reviewed and a measure of information flux through the interface is proposed. We cope with the question of why observers usually experience irreversibility in measurement processes if the evolution is reversible, i.e., one-to-one. And why should there be any meaningful concept of classical information if there is merely quantum information to begin with? We take the position here that the concept of irreversible measurement is no deep principle but originates in the practical inability to reconstruct a quantum state of the object. Many issues raised apply also to the quantum’s natural double, virtual reality. An experiment is proposed to test the conjecture that the self is transcendent.